Sirene has the appearance of a beautiful young woman with a buxom figure however her head is adorned with large bird-like wings and a pair of antenna. She also has tail feathers above her backside with her forearms and lower legs being bird-based with scales and talons.
Sirene is a prideful demon who values her power and appearance. However she is known for going to extremes to defeat enemies she abhors like Akira Fudo to the point of pairing up with former enemies and becoming a monstrosity. It takes a shake from a reminder of her love Amon to snap her out of it.
Sirene is able to fly with her large wings and can launch her arms like boomerangs and can telekinetically control them through her antenna. As a demon, she is able to fuse with matter which in this crossover includes machines like the Mechasaurs. Seemingly exclusive to this manga appearance seems to be the ability to defuse.
Sirene contacted Emperor Gore with help from other demons for an alliance for both parties to defeat their enemies Devilman and the Getter Robo. After the alliance was set and the initial demon attack was stopped, Sirene mobilized with a squad of demons fused with Mechasaurs. With the Getter Robo and Devilman each able to fend off some of the monstrosities and even fuse together, Sirene combined with their remains to become assume a more atrocious form. As the Getter Devil lock blows with the monster, Devilman separates from the configuration and convinces Sirene to defuse. Sirene reminded of Amon does so and departs vowing to kill Akira Fudo herself.